Kinetics of Cr3+ to Cr4+ ion valence transformations and intra-lattice cation exchange of Cr4+ in Cr,Ca:YAG ceramics used as laser gain and passive Q-switching media

This paper focuses on the kinetics of Cr4+ formation in Cr,Ca:YAG ceramics prepared by solid-state reaction sintering. The kinetics of Cr4+ formation was studied by annealing of Cr,Ca:YAG ceramics in ambient air under different temperatures at different times, resulting in the transformation of Cr3+...

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Published in:The Journal of chemical physics 2019-10, Vol.151 (13), p.134708-134708
Main Authors: Chaika, M. A., Tomala, R., Strek, W., Hreniak, D., Dluzewski, P., Morawiec, K., Mateychenko, P. V., Fedorov, A. G., Doroshenko, A. G., Parkhomenko, S. V., Lesniewska-Matys, K., Podniesinski, D., Kozłowska, A., Mancardi, G., Vovk, O. M.
Format: Article
Language:English
Subjects:
Activated sintering
Activation energy
Cation exchanging
Ceramics
Enthalpy
Ion exchange
Lattice sites
Oxidation
Q switched lasers
Reaction kinetics
Switching
Transformations
Trivalent chromium
YAG lasers
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Summary:This paper focuses on the kinetics of Cr4+ formation in Cr,Ca:YAG ceramics prepared by solid-state reaction sintering. The kinetics of Cr4+ formation was studied by annealing of Cr,Ca:YAG ceramics in ambient air under different temperatures at different times, resulting in the transformation of Cr3+ to Cr4+. The activation energy (Ea) of Cr3+ oxidation determined by the Jander model was 2.7 ± 0.2 eV, which is in good correlation with the activation energy of innergrain oxygen diffusion in the YAG lattice. It is concluded that Cr3+ to Cr4+ transformation in YAG ceramics is limited by oxygen diffusion through the grain body. It was established that in Cr,Ca:YAG ceramics, the intralattice cation exchange, in which the Cr4+ ions exchange positions with the Al3+ ions, switching from “A” to “D” sites, is faster than Cr3+ to Cr4+ oxidation. In the temperature range of 900–1300 °C, the reaction enthalpy of Al3+/Cr4+ ion exchange between octahedral “A” and tetrahedral “D” lattice sites is close to zero, and this exchange ratio is thermodynamically driven by entropy.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.5118321